package com.interview;

import com.alibaba.fastjson.JSON;
import com.alibaba.fastjson.JSONArray;
import com.alibaba.fastjson.JSONObject;
import org.junit.Test;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * Created by WDJ on 2019/11/4.
 */
public class Algorithm {

    /**
     * 2019-10-30号在中软国际面试被问到的
     * listToTree
     * <p>方法说明<p>
     * 将JSONArray数组转为树状结构
     * @param arr 需要转化的数据
     * @param id 数据唯一的标识键值
     * @param pid 父id唯一标识键值
     * @param child 子节点键值
     * @return JSONArray
     */
    public static JSONArray listToTree(JSONArray arr, String id, String pid, String child){
        JSONArray r = new JSONArray();
        JSONObject hash = new JSONObject();
        //将数组转为Object的形式，key为数组中的id
        for(int i=0;i<arr.size();i++){
            JSONObject json = (JSONObject) arr.get(i);
            hash.put(json.getString(id), json);
        }
        //遍历结果集
        for(int j=0;j<arr.size();j++){
            //单条记录
            JSONObject aVal = (JSONObject) arr.get(j);
            //在hash中取出key为单条记录中pid的值
            JSONObject hashVP = (JSONObject) hash.get(aVal.get(pid).toString());
            //如果记录的pid存在，则说明它有父节点，将她添加到孩子节点的集合中
            if(hashVP!=null){
                //检查是否有child属性
                if(hashVP.get(child)!=null){
                    JSONArray ch = (JSONArray) hashVP.get(child);
                    ch.add(aVal);
                    hashVP.put(child, ch);
                }else{
                    JSONArray ch = new JSONArray();
                    ch.add(aVal);
                    hashVP.put(child, ch);
                }
            }else{
                r.add(aVal);
            }
        }
        return r;
    }

    @Test
    public void testListToTree() {
        List<Map<String,Object>> data = new ArrayList<>();
        Map<String,Object> map = new HashMap<>();
        map.put("id",1);
        map.put("pid",0);
        map.put("name","甘肃省");
        data.add(map);
        Map<String,Object> map2 = new HashMap<>();
        map2.put("id",2);
        map2.put("pid",1);
        map2.put("name","天水市");
        data.add(map2);
        Map<String,Object> map3 = new HashMap<>();
        map3.put("id",3);
        map3.put("pid",2);
        map3.put("name","秦州区");
        data.add(map3);
        Map<String,Object> map3_t = new HashMap<>();
        map3_t.put("id",6);
        map3_t.put("pid",3);
        map3_t.put("name","测试镇");
        data.add(map3_t);
        Map<String,Object> map3_t1 = new HashMap<>();
        map3_t1.put("id",7);
        map3_t1.put("pid",6);
        map3_t1.put("name","测试街道");
        data.add(map3_t1);
        Map<String,Object> map4 = new HashMap<>();
        map4.put("id",4);
        map4.put("pid",0);
        map4.put("name","北京市");
        data.add(map4);
        Map<String,Object> map5 = new HashMap<>();
        map5.put("id",5);
        map5.put("pid",4);
        map5.put("name","昌平区");
        data.add(map5);
        System.out.println(JSON.toJSONString(data));
        JSONArray result = listToTree(JSONArray.parseArray(JSON.toJSONString(data)),"id","pid","children");
        System.out.println(JSON.toJSONString(result));
    }



}
